Quick acting valve



April 2, 1963 A. A. HIRST ETAL QUICK ACTING VALVE Filed Nov. 25, 1957 States atent 8 42 QUICK ACTING VALVE Arthur A. Hirst, Ashhy-de-la-Zouch, and Alan N. Burns, Burton-on-Trent, England, assignors to Coal industry (Patents) Limited, London, England, a company of Great Britain Filed Nov. 25, 1957, Sex. '0, 698,846. Claims priority, application Great Britain Nov. 30,1956; 3 Claims. cl, 251-48 This invention relates to apparatusfor filtering slurries, that is, mixtures of -a fluid with relatively finely granulated material.

Continuous vacuum filters are usually of the drum or disc typefland in such. fil-tersjt he filter. cake, thatis, the mat of fine solids formed on the surface of the drum or disc, is commonly discharged by tll application of a blast of compressed air. The admission of the compressed air for discharging the filter cake is governed by the rotation of a valve head with a plurality of ports, each port connected to one filtering compantmentof the drum or disc. Each port in turn passes a fixed port to which is connected a supply of compressed air. In this arrangement the area available for the passage of compressed air is very small in the initial stage in which the moving port first commences to overlap the fixed port, the area rises to a when the two parts are aligned and thereafter gradually becomes less. In the initial stage, when the flow of compressedair is small, the cake may crack or fairly small pieces of cake may be blown off, with the result that the stronger air flow which follows the initial stage, instead of effecting a clean discharge of the cake, escapes to atmosphere through such cracks or other paths of low resistance, leaving a substantial mat of cake adhering to the drum.

To overcome this disadvantage, in a known method the supply of compressed air is further controlled so that a quick acting valve prevents the supply or" compressed air until the fixed and moving ports are substantially aligned, at which stage the valve opens abruptly and admits a sudden blast of compressed air. Conventional types of quick acting valves rarely open fast enough to give an air blast surficiently sudden to clean discharge of filter cake. Mechanically operated quick-acting air valves may be fitted to filtens but in order to obtain a sufiiciently quick action somewhat highly stressed mechanisms may be needed and the apparatus involved is rather expensive and not easily added to an existing filter designed for discharging cake in the normal way.

An object of the present invention therefore is to provide improved apparatus to give a very sudden pulse of air, which can be timed to coincide with the period when the valve ports for admitting air are substantially fully open, which is relatively lightly stressed, and which may be simply and inexpensively added to existing filters using a normal air blow.

In apparatus constructed according to the present invention, the supply of compressed air is connected to a chamber sealed by a plate or poppet valve arranged so that the air pressure tends to hold the valve on its seat. The other side of the valve communicates with a chamber connected by a conduit, preferably short, to the air blow connection of the drum filter. Preferably a spring is interposed between the valve and a mechanism to move the valve ofi' its seat, the spring being stressed prior to the opening of the valve so that, when the valve leaves its seat and the air pressure holding it shut is suddenly relieved, the valve is quickly accelerated open by the spring. It will be understood that the term spring includes one or more resilient helical wire coils or other resilient elements actin in compression and/or in tension to impart the desired rapid opening motion to the valve.

The movement of the means actuating the spring may be smooth andrelatively slow so that the actuating mechanism is lightly stressed and in a preferred arrangement may be a diaphragm motor actuated by relatively low pressure compressed air from the. same source as that used for discharging the. filter cake.

An advantage of the invention is that the mechanism for actuating *thevalve may. move. relatively. slowly, as the sudden acceleration of the air control valve results from the action of the spring and the. sudden relief of the air pressure holding-the valve on itsseat, and is not directly connected with the rate of movement ofthe mechanism used for stressing the spring, A further advantage of the invention is that, as a result of the relatively small force required to actuate the mechanism forstressing the said spring, it is. possible to dispense with the normal power drive embodying gears or roller chains, whichare necessary to actuate a more highly stressed mechanism. It is frequently relatively difiicult and expensive to fit such power drives to existing rotary filters which havenqt been originally designed to give a sudden Iblast,

By Way of example the invention is illustrated in the accompanying drawing which shows a quick acting valve constructed in accordance with the present invention.

Referring to the said drawing, a chamber *1 has an, inlet connection 2 connected to a conduit to a receiver for a supply of compressed air. Preferably the said conduit is short. The chamber 1 may be. sealed by a plate valve 3 seating-on a rubber ring 4. Preferably the plate valve 3 is not rigidly located, so that a small degree of malalignment does not interfere with its sealing on the rubber ring 4. The compressed air supplied to the chamber tends to hold the valve 3 in its closed position on its seating 4. A coil spring 5 is arranged for compression by an enlargement 6 of the operating rod 7 of a diaphragm motor 8. When air is supplied to the inlet connection g of the diaphragm motor its pressure plate 10 moves the operating rod so as to compress the spring 5. When the rod 7 commences to move, the force exerted by the spring 5 is insufiicient to overcome the air pressure holding the valve 3 on its seating. The rating of the compression spring 5 is such that it is insuificiently strong to cause the valve 3 to leave its seating, but the extremity 11 of the operating rod 7 is caused to thrust against a shim 12 in contact with a plate on the valve 3. It is to be understood, of course, that, if the diaphragm motor 8 uses compressed air from the supply connected to chamber 1, the pressure plate 10 must be significantly larger than the valve 3. When the valve 3 is opened by the thrust of the extremity 11 of the operating rod 7 against the shim 12, the valve is rapidly accelerated by the spring compression. The suddenly accelerated opening of the valve 3 is terminated when the valve 3 comes into contact with the rubber pad 13 which provides a cushioning effect because of the resilience of the rubber pad, the relatively large areas involved, and the compression of air between the pad 13 and the valve 3.

It is to be understood that Where reference is made to rubber, other resilient materials may alternatively be used. Adjusting shims may be provided between the shim l2 and the valve 3 to vary the initial compression of the spring 5 and at the same time to vary the clearance between the tip 11 of the operating rod 7 and the shim 12. Adjusting washers may also be used between the enlargement 6 of the operating rod 7 and the spring 5 to vary the initial compression of the spring 5 Without affecting the clearance between the tip of the operating rod and the shim 12. It is to be understood, moreover, that provision may be made for varying the position or thickness of the pad 13.

When the valve 3 is open the chamber 1 is connected to a further chamber 16 connected by an outlet 17 by a pipe or conduit (which is preferably short) to the air blast connection of the filter. In one arrangement the chamber 16 may be further connected to a one-Way atmospheric valve arranged automatically to relieve any partial vacuum in the filter compartment connected to outlet 17 during the period whilst the air blast ports of the filter are opening, but prior to the sudden opening of the quick'acting valve 3. The operating rod 7 moves through one end of the chamber 16 and escape of air is sealed by labyrinth washers 18 or other appropriate sealing means.

Subsequently to the admission of air lrom chamber 1 to chamber 16 the supply of air to the diaphragm motor 8 is interrupted and the air contained in the diaphragm is exhausted to atmosphere, whereupon the diaphragm spring 19 causes the valve 3 to return to its setting on which it is pressed by air entering the chamber 1.

We claim:

1. A valve comprising a valve housing forming an inlet chamber, an outlet chamber, a valve seat defining a port between said inlet chamber and said outlet chamber, a valve disc of substantial area releasably engageable with said seat and normally held against said seat to close said port by pressure in said inlet chamber, a pushing rod axially movable within said outlet chamber, a tube secured to said valve disc and having an end wall member slidably receiving said pushing rod, said rod having an enlargement inwardly adjacent said end wall rnemben a coiled spring in said tube surrounding said pushing rod and bearing between said valve disc and said enlargement, pneumatically operated valve-opening means movable into engagement with said pushing rod to release said disc from engagment with said seat, said coiled spring being adapted to be stressed by axial movement of said pushing rod while said disc remains in engagement with said seat and for rapidly accelerating movement of said disc in a direction opposite to that of passage of fluid through said port when the disc is released from engagement with said seat, and a butter of substantial area mounted in said inlet chamber in the path of movement of said disc in said direction, the operative face of the buffer having an area substantially equal to the area of said disc on the inlet side thereof and being in axial alignment with and parallel to the said area of said disc, whereby movement of said disc in said direction is retarded by a cushioning effect created by the compression of a volume of fluid between said face of the disc and said operative face of said butter.

2. The structure of claim 1, and guide means disposed within said inlet chamber, said guide means comprising a plurality of spaced guide members secured to said seat and extending inwardly into said inlet chamber and having straight guide edges located adjacent the peripheral edges of the disc and extending parallel to said tube.

3. The structure of claim 2, and wherein said straight guide edges extend substantially to the plane of said butler.

References Cited in the file of this patent UNITED STATES PATENTS 1,963,684 Shimer June 19, 1934 2,319,964 Wilson May 25, 1943 2,435,235 Porter Feb. 3, 1943 2,459,527 Herbert Jan. 18, 1949 2,520,386 Dillman Aug. 29, 1950 2,564,569 Goehring Aug. 14, 1951 2,797,061 Buchanan June 25, 1957 2,872,149 Battey Feb. 3, 1959 

1. A VALVE COMPRISING A VALVE HOUSING FORMING AN INLET CHAMBER, AN OUTLET CHAMBER, A VALVE SEAT DEFINING A PORT BETWEEN SAID INLET CHAMBER AND SAID OUTLET CHAMBER, A VALVE DISC OF SUBSTANTIAL AREA RELEASABLY ENGAGEABLE WITH SAID SEAT AND NORMALLY HELD AGAINST SAID SEAT TO CLOSE SAID PORT BY PRESSURE IN SAID INLET CHAMBER, A PUSHING ROD AXIALLY MOVABLE WITHIN SAID OUTLET CHAMBER, A TUBE SECURED TO SAID VALVE DISC AND HAVING AN END WALL MEMBER SLIDABLY RECEIVING SAID PUSHING ROD, SAID ROD HAVING AN ENLARGEMENT INWARDLY ADJACENT SAID END WALL MEMBER, A COILED SPRING IN SAID TUBE SURROUNDING SAID PUSHING ROD AND BEARING BETWEEN SAID VALVE DISC AND SAID ENLARGEMENT, PNEUMATICALLY OPERATED VALVE-OPENING MEANS MOVABLE INTO ENGAGEMENT WITH SAID PUSHING ROD TO RELEASE SAID DISC FROM ENGAGEMENT WITH SAID SEAT, SAID COILED SPRING BEING ADAPTED TO BE STRESSED BY AXIAL MOVEMENT OF SAID PUSHING ROD WHILE SAID DISC REMAINS IN ENGAGEMENT WITH SAID SEAT AND FOR RAPIDLY ACCELERATING MOVEMENT OF SAID DISC IN A DIRECTION OPPOSITE TO THAT OF PASSAGE OF FLUID THROUGH SAID PORT WHEN THE DISC IS RELEASED FROM ENGAGEMENT WITH SAID SEAT, AND A BUFFER OF SUBSTANTIAL AREA MOUNTED IN SAID INLET CHAMBER IN THE PATH OF MOVEMENT OF SAID DISC IN SAID DIRECTION, THE OPERATIVE FACE OF THE BUFFER HAVING AN AREA SUBSTANTIALLY EQUAL TO THE AREA OF SAID DISC ON THE INLET SIDE THEREOF AND BEING IN AXIAL ALIGNMENT WITH AND PARALLEL TO THE SAID AREA OF SAID DISC, WHEREBY MOVEMENT OF SAID DISC IN SAID DIRECTION IS RETARDED BY A CUSHIONING EFFECT CREATED BY THE COMPRESSION OF A VOLUME OF FLUID BETWEEN SAID FACE OF THE DISC AND SAID OPERATIVE FACE OF SAID BUFFER. 